Method and apparatus for making electrolyzed water

ABSTRACT

An insulating end cap for a cylindrical electrolysis cell the type comprising at least two tubular electrodes with a cylindrical membrane arranged co-axially between them, comprises a first annular section with first and second axial ends, having at its first axial end a circular seating or one end of an outer cylindrical electrode and at its second end a circular aperture, of smaller diameter than the circular seating and co-axial therewith, to accommodate one end of the membrane. A second annular section of the end cap is detachably secured to the first and has a central circular aperture of smaller diameter than the central aperture of the first section and co-axial therewith, to accommodate one end of the inner cylindrical electrode. The two part construction of the end cap facilitates the assembly of the cell, and reduces the likelihood of breakage of the fragile ceramic membrane.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an insulating end cap construction for acylindrical electrolysis cell of the type comprising at least twotubular electrodes arranged coaxially, one within the other, with acylindrical membrane arranged coaxially between them.

2. Description of the Prior Art

Cells of the type to which the invention relates can be used for examplefor sanitising water through electrolysis for drinking purposes, orelectrolysing brine solutions to make a powerful biocide. Many types ofelectrochemical activation and electrolysis cells exist for thispurpose, and generally comprise two concentric cylindrical electrodes,one of which acts as a cathode and the other as an anode, anion-permeable membrane being located coaxially between them to separatethe space between the electrodes into anode and cathode compartments. Anelectrolyte such as brine is passed through the anode and cathodecompartments, separately or successively. When brine is electrolysed inthis way, under suitable conditions, it can produce a sporicide solutionof high strength and long shelf life, which is ecologically and humanfriendly.

One type of concentric cylindrical cell of the type to which theinvention relates is disclosed in published European Patent ApplicationNo. 922788. This discloses an electrolytic cell in which the twoconcentric electrodes and the membrane are received in unitary endbushes, each having a central aperture for passage of the innerelectrode with surrounding concentric seatings for the membrane and theouter electrode. Cells of this type function quite well, but a problemarises in their construction. A high degree of craft skill is requiredto assemble them, and in particular to assemble the cell components inthe end bushes, and there is a high breakage rate. With brittle ceramiccylindrical membranes, damage rates can be as high as 1 in 5.

It is accordingly an object of the present invention to provide an endcap for an electrolytic cell which is easy to fit and reduces thelikelihood of breakages.

It is another object of the present invention to provide a cylindricalcell which is leak-free and pressure-resistant. Many existing cellsstart leaking over a period of time as component parts are mechanicallysealed with gaskets. During the lifetime of a cell, component partsbecome brittle, shrink or expand, causing leakages.

SUMMARY OF THE INVENTION

The present invention provides an insulating end cap for a cylindricalelectrolysis cell of the type comprising at least two tubular electrodesarranged coaxially one within the other with a cylindrical membranearranged coaxially between them, said end cap comprising:

a first annular section of insulating material with first and secondaxial ends, having at its first axial end a circular seating for one endof an outer cylindrical electrode and at its second end a circularaperture, of smaller diameter than said circular seating and coaxialtherewith, to accommodate one end of a cylindrical membrane; and

a second annular section of insulating material detachably secured tothe first and having a central circular aperture, of smaller diameterthan the central aperture of the first section and coaxial therewith toaccommodate one end of an inner cylindrical electrode.

With the insulating end caps of the invention, the assembly of the cellcan be greatly simplified, avoiding damage to components and allowingeasier visual inspection at all stages of construction. Craft skills arenot necessary, and sealants can more easily be used, avoiding the needfor mechanical gasket or O-ring seals. The use of such non-toxicsealants helps to avoid leakages and imparts increased pressureresistance.

The sealants and the end caps can be made of a plastics material that isapproved for medical purposes, and can be in contact with drinkingwater. The preferred sealants are two-part epoxy sealants which possessa high chemical resistance as well as a high degree of flexibility, sothat seals are maintained even when components shrink or expand duringthe electrolysis process.

The second annular section is preferably secured to the first by meansof a screw thread. This means that the end cap can be assembled andsecured to the cylindrical cell components without the need to applyforce to overcome friction.

In a preferred embodiment of the invention, a third annular section issecured to the second section, this third section having a centralcircular aperture of similar diameter to that of the aperture in thesecond section and serving to enhance a sealing engagement between theend cap and an inner cylindrical electrode passing through saidapertures of the second and third sections. This third section ispreferably secured to the second section by means of a screw thread, forthe same reasons as discussed above in connection with the first andsecond sections.

One or both of the first and second sections of the end cap may beprovided with lateral inlets through their outer walls, for the passageof electrolyte into or out of the cell compartments defined between theelectrodes and the membrane. In the first section, the inlets can beprovided axially between the seating for the first electrode and thecircular aperture through which the membrane passes. In the secondsection the inlet can be provided axially between the first and secondends. In each case the lateral inlets are preferably arranged fortangential feed into the cell compartments so that a spiral flow patternof the electrolyte through the anode or cathode chamber is achieved.

The electrolyte inlets are preferably equipped with John Guest fittingsfor sealing connections to electrolyte inlet or outlet pipes.

According to a further aspect of the invention, there is provided acylindrical electrolysis cell comprising at least two tubular electrodesarranged coaxially, one within the other, with a cylindricalion-permeable membrane arranged coaxially between them, wherein there isprovided at least one end of the cell an insulating end cap as definedabove, one end of a radially outer electrode of the cell being locatedin the circular seating at the first end of the first annular section,one end of the cylindrical membrane being located in the circularaperture at the second end of the first section and one end of an innertubular electrode being located in the central aperture of the secondsection. This arrangement is preferably provided at both ends of thecell.

The cell membrane is preferably a ceramic ion-permeable membrane, morepreferably comprising alumina and/or zirconia. One preferred type ofmembrane comprises Al₂O₃ particles with a mean particle size of 3 to 5μm and ZrO₂ particles with a mean particle size of 0.3 to 0.8 μm. Thepreferred ratio of Al₂O₃ to 5 wt % of Al₂O₃ and 15 wt % ZrO₂. The endcap construction of the present invention means that relatively fragilemembranes can be used. The membrane preferably has a thickness of 1-2mm. The membrane can be made as a slip and fixed in cylindrical form.

Conventional electrolysis cells of the type to which the inventionrelates typically have an anode made of titanium, the cathode being of adifferent metal. In the preferred embodiments of the present invention,both the anode and the cathode can be made from titanium, and at leastthe anode is preferably coated with a mixed oxide for enhancedperformance. In more preferred embodiments, both the anode and thecathode are made from titanium and coated with a mixed oxide. Thepreferred coating structures are made from platinum or platinum metaloxides, which may be mixed with other transition metal oxides. Preferredcoatings will be discussed in more detail below.

Various different biocidal liquids can be produced in the electrolysiscells of the present invention, depending on the pipework configuration(flow pattern through the cell). For example, the electrolyte can be fedto the anode and cathode compartments and the electrolysed liquid canthen be collected from each of these compartments separately.Alternatively, the electrolyte can be fed through both electrodechambers successively. Other factors which can be used to vary thebiocidal liquid include the voltage applied to the electrodes, theelectrical power absorbed, the electrode coating and physical size ofthe electrode, the shape of the electrodes and distances between themand the spacing and material of the membrane. The membrane material isalso an important feature since it affects the mobility of ions passingbetween the electrodes.

The preferred mixed oxide coated electrodes comprise a titanium baseactivated with a coating structure which may comprise platinum,preferably in finely divided form such as platinum black, or platinummetal oxide mixed with oxides of one or more other transition metaloxides such as those of titanium, tantalum, niobilum, iridium,ruthenium, rhodium or palladium oxides, or mixtures thereof. Theparticular coating selected will depend on the application. Bydepositing a number of layers, one upon the other, a noble metal mixedoxide coating can be obtained on the titanium substrate. Each layer maybe less than 1 μm thick. In a preferred process for reducing thecoatings, the metal compounds are dissolved in organic solvents, appliedto the surface and decomposed after drying. The titanium base is thusshielded and an electrode is obtained with a small internal resistance,high loading capacity for the electric current, a constant electrodepotential over the life of the electrode and a low rate of wear.

When the electrode is to be used for the electrolysis of brine, forexample sea water, for the production of biocidal liquids the preferredcoating is a ruthenium mixed metal oxide or a platinum-iridium oxidecoating on the titanium anode, depending on for example the temperatureof the sea water and its salinity.

Where the electrolyte feed liquid comprises a brine feed of mains watermixed with sodium chloride for the production of biocidal liquids, aruthenium mixed metal oxide coating is preferably applied to thetitanium electrode. This is to ensure an optimal conversion ofelectrolyte into biocidal liquid. Deposits of electrolyte or brine inthe biocidal liquid are minimised, and the content of active chlorine ismaximised.

For sanitising water in order to make a sterile anti-oxidant drink, thepreferred electrodes are coated with a platinum-iridium oxide coating ora ruthenium mixed metal oxide coating. This is to ensure the maximumproduction of oxygen within the electrolytic cell.

The biocidal liquids produced in the electrolytic cell can have a pHvarying from 2 to 8.5 and an essentially positive redox potential,typically in the range from +600 to +1200 mV. Alternatively, a wettingalkaline liquid can be produced with a strongly negative redoxpotential, typically in the range from −800 mV to

−1100 mV, depending on the conditions applied to the cell.

The negatively charged alkaline liquids are not stable and last only forabout 48 hours before losing their charge. They have been used as apowerful anti-oxidant within the bodies of fish and mammals to boost theimmune system. They have many other uses. The positively chargedbiocidal liquids can be sustained in what are stable solutions for up totwo years given certain production conditions within the electrolyticcell. Although many large users of biocides may find it advantageous tomanufacture fresh biocidal liquids, it can be shown that a sporicidaleffect can be achieved with biocidal liquid blends for up to fivemonths.

This invention sets out to produce an electrolytic cell with some uniquefeatures that address the problems of robustness, general reliability,cost, performance, ease of manufacture and quality control (traceabilityand usage of approved materials).

Some particular applications of the cells of the present invention willnow be described.

Electrochemical Activation of Mineralised Water

The system used allows for two things to happen:

(1) It sterilises the water passing through the cell housing.

(2) It imposes an electrical charge on the water passing through thecell housing.

Sanitising water for drinking purposes is achieved using a diaphramaticelectrolyses cell and an active-coal filter, in which water is purifiedin several stages:

First stage is the oxidation of water and its substances. Bacteria,viruses and organic substances are destroyed (oxidised). The water issaturated with short-lived oxidants, such as HClO, ClO₂, O₃, O₂, H₂O₂,OH.

The second stage takes place in a reaction chamber, where oxidationprocesses continue. The third stage consists of catalytic destruction ofactive chlorine compounds; removal of organic substances, taste andtaint using activated coal as a sorbent.

The final stage consists of reduction of tap water and its substances.Toxic heavy metal ions and hazardous organic substances such asherbicides, pesticides, phenols and dioxins are transformed intonon-toxic hydroxyls. The water is saturated with anti-oxidants: OH⁻, HO₂⁻ and O₂.

Electrolysis of water take place at the surface of mixed-oxide noblemetal coated electrodes within the electrolytic cell. Free radicals arereleased during electrolysis like hydroxyls, oxidants, such as oxygenand ozone to sanitize the water passing through the anode and cathodechamber of an electrolytic cell. In order to “plate” out metals andbreak down organic molecules into harmless components an anthracite andactivated carbon chamber are fitted next to the electrolytic cell. Partof this sanitizing process puts a predominantly negative charge on thewater. This property makes the water an anti-oxidant. Anti-oxidants havemany uses.

The two main properties listed give this technology a wide range ofuses:

(1) Sterilisation and purification of water sources.

(2) Potable/hot water systems/water features;

(3) Additive in the food industry harnessing the anti-oxidantproperties.

(4) As a fodder assimilator and health promoter in pigs and poultry.

(5) As a skin treatment for a range of dermatitis disorders.

(6) As a health drink for humans (anti-oxidant booster of the immunesystem).

To serve the needs outlined above where the quantity requirements arediverse a simple robust system for making the desired water is required.This invention seeks to use a standard cylindrical electrolysis cellwhich has been developed for water or brine electrolysis. Take advantageof the modular nature of the electrolytic cell and try to create anelectrochemical activation process which can be tailored to address themany diverse applications.

Electrolysis of Brine

This electrochemical activation of a brine solution is achieved using acylindrical diaphragm electrolysis cell (an electrolytic cell).

The electrolytic cell can produce various biocidal liquids, depending onthe electrical power supply, the current drawn, brine feed and flowpattern convention.

In the cathode chamber, e.g. the following reactions take place:2H₂O+2^(e)=H₂+2OH⁻2H₃O+2^(e)=H₃+2H₂O₂

In the anode chamber, e.g. the following reactions take place:2Cl═Cl₂+2^(e)3H₂O═½O₂+2H₃O⁻+2e ⁻2OH═½O₂+H₂O+2eand the formation of active chlorine:Cl₂+H₂O+HClOHClO+H⁺+ClOAs well as the formation of hypochlorite, as minor by-product:HClO+NaOH═NaClO+H₂O

Several cylindrical cells exists where a water or brine solution to beprocessed flows upwards through valves in the lower part of theelectrolysis cell. Electrochemically received anolyte and catholyteleave the electrolysis cell by separate channels in the upper part ofthe electrolysis cell. The disadvantage of these electrolysis cells isthe possibility of gas-filled zones forming in the upper part ofelectrode chambers, so that considerable losses of electricity occurwhich are due to counter-flow of electrochemically obtained gases andelectrolytes.

When the electrolytic cells of the invention are used for electrolysisof the potable water, water to be electrolysed is preferably supplied toboth chambers in the lower part of an electrolytic cell, and the anolyteand catholyte received are removed separately from the upper parts ofthe separated chambers.

A spiral feed of electrolyte into the anode and cathode chambers leadsto turbulization of the electrolytes in the chambers of the electricalcell, prolongs influence of electrolysis over elementary amounts of theprocessed water solutions, simplifies removal of gaseous and liquidproducts of electrolysis and reduces possible formation of gas-filledzones in the upper points of electrode chambers.

The space between outer cylindrical electrode and membrane, and betweenmembrane and inner cylindrical electrode form separated electrodechambers whose geometric dimensions preferably satisfy the following:D_(D)≧0.835D_(S)D_(B)≧0.695D_(S)D_(S)—inner diameter of outer cylindrical electrode, mm;D_(D)—inner diameter of membrane, mmD_(B)—outer diameter of inner cylindrical electrode, mm

In terms of surface area the relation between the anode and the cathode(ion exchange area) should preferably be roughly 1:1.40-1:1.50respectively with a spacing between the electrodes (separated from themembrane) of 9 mm to 21 mm depending on the capacity of the electrolyticcell and the product requirements. The length of the ion exchange areacan be varied depending on the volume required.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects and advantages of the invention will become apparentfrom the following detailed description, when read with reference to theaccompanying drawings which illustrate preferred embodiments thereof.

In the Drawings:

FIG. 1 is a side elevation of an electrolytic cell having a pair ofmultiple end caps according to the present invention;

FIG. 2 is a cross-section on the line II-II of FIG. 1;

FIG. 2 a is an enlarged detail of a part of FIG. 2;

FIG. 3 is a partially cutaway bottom plan view of the cell of FIG. 1;

FIG. 4 is a partially cutaway plan view of a first section of one of theend caps of the cell of FIG. 1;

FIG. 5 is a cross-section on the line V-V of FIG. 4;

FIG. 6 is a partially cutaway plan view of the second section of amodification of one of the end caps of the cell of FIG. 1;

FIG. 7 is a cross-section on the line VII-VII of FIG. 6; and

FIG. 8 is a schematic flow diagram of an electrolytic process usingcells in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIGS. 1 and 2, a cylindrical electrolysis cellgenerally indicated by 10 comprises an outer cylindrical anode 12enclosed on its outer surface by a cylindrical protective and insulatingsleeve 14. This electrode is preferably made of titanium, coated on itsinner surface with a transition metal oxide coating as described above.An inner cylindrical cathode 16, also preferably made of titanium andwith a transition metal oxide coating on its outer surface, is arrangedco-axially within the cylindrical anode, and a cylindrical ion-permeablemembrane 18 is arranged co-axially between the electrodes in such a wayas to define a space 20 between the anode and the membrane, which in useacts as an anolyte compartment, and a space 22 between the membrane andthe cathode, which in use becomes the catholyte compartment.

The ion-permeable membrane 18 is preferably a ceramic membrane, and issuitably made from allumina.

An insulating end cap 23 is provided at each end of the cell, the endcaps each comprising three annular sections which are co-axial with oneanother and secured together by means of screw threads. The threesections 24, 32 and 36 can best be seen in FIG. 2. The first annularsection 24 has three circular apertures 26, 28 and 30. The aperture 26is surrounded by an annular end face 27, against which bears one end ofthe insulating sleeve 14.

The aperture 26 has an inner diameter which matches the outer diameterof the cylindrical anode 12, and is separated from the aperture 28 by anannular shoulder 27, lying in a plane perpendicular to the longitudinalaxis of the cell, and which acts as a seating for one end of thecylindrical anode 12.

The innermost circular aperture 30 of the first annular section has aninner diameter such as to match the outer diameter of the membrane 18,such that the membrane can be slid into this section without the need toovercome substantial friction but without significant play when it is inposition.

A second annular section 32 of insulating material is detachably securedby a screw thread 33 to an end of the first section 24 which is remotefrom the seating 27 for the anode. This annular section has a circularrecess within it, which is of larger diameter than the membrane 18, sothat the second section can be screwed onto the first without touchingthe membrane, which may be projecting axially beyond the first section.

At its opposite axial end the second section of the end cap has acircular aperture 34 which accommodates one axial end of the cylindricalcathode 16.

The third annular section 36 is detachably secured to the second annularsection 32 by means of a screw thread 39, and has a central circularaperture 38 of similar diameter to that of the second section. The thirdannular section serves to enhance a ceiling engagement between the endcap 23 and the cathode 16.

As can be seen in FIG. 2 a, the central circular aperture 34 of thesecond annular section 32 has a circumferential channel 41 accommodatinga ceiling ring 43 to enhance the seal between the second section and thecathode 16.

A radially projecting terminal 48 is provided for the anode 12, abouthalf way along its axial length, and a similarly shaped terminal 50 isprovided at one axial end of the cathode 16.

The two end cap assemblies at opposite ends of the cell are essentiallythe same, and each has a pair of John Guest fitting for ceilingconnections of inlet and outlet pipes for electrolytes. Each of thesefittings connects to a lateral inlet through one of the annular sectionsof the end caps, transverse to the longitudinal direction of the celland offset from the central axis of the cell.

At the lower end of the cell, an inlet fitting 40 passes through thefirst annular section of the end cap to the space 20 which forms theanode chamber. At the upper end, a corresponding fitting 44 is providedas an outlet connection from the anode chamber.

A John Guest fitting 42 at the lower end of the cell provides an inletconnection through the second end cap section 32 to the anode chamber,and at the upper end of the cell a corresponding fitting 46 provides anoutlet connection from the anode chamber.

The bottom plan view of FIG. 3 shows the electrolyte inlets in moredetail. The John Guest fitting 40 connects to an inlet tube 52 whichpasses tangentially through the first section 24 of the lower end cap tocommunicate with the anode chamber 20 through an aperture 56.

Similarly, John Guest fitting 42 connects to an inlet pipe 54 through anaperture 58 in the second section 32 of the end cap, to feed electrolyteinto the cathode chamber 22. A similar arrangement at the upper end ofthe cathode chamber 22 provides an outlet from the chamber through aJohn Guest fitting 46.

The inlet tubes 52 and 54 enter the respective anode and cathodechambers tangentially to impart a spiral motion to the electrolytepassing through each of the chambers. This enhances mixing of theelectrolyte, with consequent benefit to the electrolysis process.

The structure of the first section 24 of the end cap is shown in moredetail in FIGS. 4 and 5, which show the screw thread 33 at the secondend of the section, the three co-axial apertures 26, 28 and 30 and theshape of the tangential inlet ball 56 where it enters the aperture 28.Also illustrated is the shoulder 27 which acts as a seating for theaxial end of the anode.

FIGS. 6 and 7 show a plan view of the second end cap section 32, fromthe side which connects to the first section. This shows the inside ofthe screw thread 33 and the inner aperture 34, as well as the tangentialinlet 58 for the electrolyte. The cross-sectional view 7 also shows thescrew thread 39 to which the third end cap section is attached.

In the version shown in FIG. 7, instead of an annular channel 41 toreceive an O-ring, there is an open seating 60 so that an O-ring orother type of annular seal can be compressed by screwing on the thirdend cap section.

A two pack epoxy sealant is used to seal around the axial ends of theanode 12 where it seats in the end cap first section 24, around theoutside of the axial ends of the membrane where they are received in theaperture 30 of the end cap first sections and around the axial ends ofthe cathode 16 where they are received in the apertures 34 of the secondend cap sections.

The ceramic ion permeable membrane should preferably have a lowhydraulic resistance and a high mechanical strength. The porosity andthe pore size of the ceramic are important for electrolysis and dependon the nature of the particles in the slurry.

In one preferred process, ceramic ion permeable membranes can bemanufactured by cast forming a slurry of a mixture of non-metallicand/or metallic particles in a porous mould. A slurry contains fineparticles, but the majority are coarse particles. Most commonly usedmaterials for the particles are alumina, mullite and zirconium-dioxide,but other materials can be used to give the membrane specificcharacteristics. After the slurry is applied to a porous mould, theslurry is fired at a temperature between 1100-1300° C. Firing isexecuted in a controlled environment in order to sinter the membranewithout formation of cracks due to shrinkage and differences in thethermal expansion coefficient of the particles.

FIG. 8 shows an example of an electrolyser system and a typical flowthrough such a system. The process of the present invention may beoperated as illustrated by and with reference to FIG. 8 as follows:

A water supply 70, such as towns water, is fed via an optionalpre-heater 72 which is typically controlled at from 30 to 40° C. throughfeed lines around which are wound aerials of a low band frequency radiowave transmitter 74. The water is optionally passed through a hard saltdeioniser 76. The towns water supply feeds both the mixer column 78, andthe brine tank 80. The towns water supply to the mixer column 78 is usedto dilute the brine solution feed. The towns water supply to the brinetank is used to prepare the brine solution, typically from sodiumchloride and towns water. The towns water feed line has a T-connector 75to direct the towns water feed to the mixer column and to the brinetank. A first valve 77, in a first feed line after the T-connector inthe towns water feed line controls the flow of towns water to the mixercolumn 78; a second valve 79, in a second feed line after theT-connector 75, in the towns water feed line controls the flow of townswater to the brine tank. Regulation of these valves controls the flow oftowns water to the mixer column and to the brine tank. A secondT-connector 81 is situated downstream of the valve 77 between the townswater supply and the mixer column. A feed line from the brine tank 80,via this second T-connector, provides a supply of brine, via a thirdvalve 82 to the mixer column 78. Regulation of the first and thirdvalves allows the concentration of brine fed to and exiting from themixer column to be controlled. It will be appreciated that closing thethird valve 82 will isolate the brine feed to the mixer column andresult in only towns water being fed into the mixer column. It will alsobe appreciated that the first, second and third valves may be automatedand controlled in response to a suitable signal from the electrolysersystem. For example, the second valve 79 may be controlled by a leveldetector 83 in the brine tank, the valve closing when a particularpre-set level is reached. The first and third valves 79, 82 may becontrolled by a suitable means such as a conductivity detector 84situated before or after the mixer column which adjusts the relativeflows of towns water to obtain a pre-set range of conductivity. Furtherthe first and third valves may be controlled by a redox meter or pHmeter measuring the redox or pH value of the liquid medium exiting theelectrolyser(s) (E). In this example the feed liquid exiting the mixercolumn 78 is caused to flow into the anode chamber 85 of the firstelectrolyser 90 and from the anode chamber to the cathode chamber 88 ofthe first electrolyser. The liquid exiting the cathode chamber 88 of thefirst electrolyser is caused to flow into the anode chamber 92 of asecond electrolyser 91 and from the anode chamber to the cathode chamber94 of the second electrolyser. On its way from the mixer column to thefirst electrolyser the feed liquid is subjected to further radio wavesfrom a generator 86.

The liquid medium exiting the electrolyser, or if more than oneelectrolyser the last electrolyser 91, is caused to flow into a gasentrainment column 95 where gases such as hydrogen, oxygen, ozone andchlorine which are produced in the process are disengaged. The gasentrainment column, is typically made of glass or plastics materialwhich is packed with an inert support, such as plastics rings.A non-foaming non-ionic surfactant held in a surfactant tank 100 may befed into the liquid medium exiting the electrolyser 90 either before orafter the gas entrainment column 95 (shown as before in FIG. 8). Thesurfactant may be fed into the liquid medium via a T-connector 102 andusing a suitable pump, such as a peristaltic pump, to transfer thesurfactant. The liquid medium exiting the gas entrainment column isready for use as a broad spectrum biocide in sterilization,disinfection, and bio-film removal applications and the like.A central power supply and control unit 150 controls the power supply tothe electrolysers 90, 92 via transformers 152, 154, and also controlsthe operation of the valves and radio wave generators.It will be appreciated that any number of electrolysers may be operatedin series or in parallel as part of the electrolyser system. It will befurther appreciated that the pipework connecting the electrolysers maybe arranged in different ways to provide liquid media with differentcharacteristics.In a second example the liquid medium exiting the anode chamber iscollected via an outlet from the anode chamber (not shown in FIG. 8).In a third example part of the liquid medium exiting the anode chamberis collected and part is fed into the cathode chamber via a T-connectorand outlet (not shown in FIG. 8). In a fourth example the feed liquidexiting the mixer column 78 is fed via a manifold device intoelectrolysers connected in parallel.

When the electrolyte is fed successively through the anode and cathodechamber of one or more cells in accordance with the invention, theresulting solution is known as “anolyte neutral (ANK) solution”. Thistypically has a pH between 7 and 8.9, preferably 7.7+/−0.5. In this modeof operation, a rectified square wave direct current is applied acrossthe electrodes. The electrical system applies a steady current based onthe saline content of the brine flowing through the cell. This is set tocertain working perimeters. The current is preferably at least 20 amps,depending on the volume and length of the cell, to ensure a goodsporicidal liquid flow. Minimum brine concentrations ensure that theresidues in the product are at a minimum. Brine feeds to the cell of 5to 15 millisiemens (3 to 12 g/l) with a product concentration of 6 to 16millisiemens (4 to 13 g/l). To preserve the life of the cell, therunning temperature that is generated should be below 55° C. Theelectrical system is self monitoring in terms of working perimeters andalso has a reverse polarity feature. This enables any surfacecontamination to be removed, and can be activated as desired, especiallywhen running in a neutral product mode.

When running the system to produce purified water, a mineralised waterfeed with a TDS of about 300 microsiemens (0.3 g/l) is enough to drawsufficient current (at least 2.5 amps) to ensure that the product isgerm free and negatively charged to −100 milli-volts on the redox meter.The voltage applied can be varied according to the mineralisation of thewater, which should not be less than 250 microsiemens (0.25 g/l).

1. A method of making an electrolyzed liquid comprising: providing anelectrolysis cell comprising an outer tubular electrode separated froman inner tubular electrode by a tubular ion permeable membrane arrangedcoaxially one within the other and a pair of end caps where the spacebetween the inner tubular electrode and the membrane and the spacebetween the membrane and the outer tubular electrode defines anode andcathode compartments where one of the electrodes functions as an anodeand the other electrode functions as a cathode; providing a liquidcomprising water or brine to the electrolysis cell and while in theelectrolysis cell is contained within the anode and cathode compartmentsand the end caps; and applying a current across the electrodes, whereineach end cap provides a sealing engagement between the end cap and eachof the inner tubular electrode, the outer tubular electrode, and themembrane, wherein the end cap has a lateral inlet through an outer wallthereof, said inlet being provided with a fitting for tangential feedingof the liquid to the inside of the end cap, and wherein the end capcomprises: a first annular section of insulating material with first andsecond axial ends, having at its first axial end a circular seating forone end of the outer cylindrical electrode and at its second end acircular aperture, of smaller diameter than the circular seating andcoaxial therewith, to accommodate one end of the cylindrical membrane,and a second annular section of insulating material detachably securedto the first annular section and having a central circular aperture, ofsmaller diameter than the central aperture of the first annular sectionand coaxial therewith to accommodate one end of the inner cylindricalelectrode.
 2. The method of claim 1, wherein the ion-permeable membraneis a ceramic membrane.
 3. The method according to claim 1, wherein theion-permeable membrane comprises alumina, zirconia, or a mixturethereof.
 4. The method according to claim 1, wherein the ion-permeablemembrane comprises a ceramic a transition metal oxide that is an oxideof a transition metal selected from the group comprising of titanium,niobium, tantalaum, iridium, ruthenium, rhodium, palladium and mixturesthereof.
 5. The method according to claim 1, wherein the anode andcathode, or both, comprise a titanium base activated with a coatingstructure comprising platinum and at least one other transition metaloxide.
 6. The method according to claim 5, wherein said at least oneother transition metal oxide is an oxide of a transition metal selectedfrom the group comprising of titanium, niobium, tantalaum, iridium,ruthenium, rhodium, palladium and mixtures thereof.
 7. The method ofclaim 1, wherein the liquid is brine and the method further comprises,isolating a biocidal liquid, a sporicidal, or both, having a pH rangingfrom 2 and 8.5 and a positive redox potential ranging from 600 to 1200mV.
 8. The method of claim 1, wherein the liquid is brine and the methodfurther comprises, isolating an alkaline biocidal liquid having anegative redox potential ranging from 600 to 1200 mV.
 9. The method ofclaim 1, wherein a portion of the liquid exiting the cathode chamber isfed into the anode chamber.
 10. The method of claim 1, wherein theliquid is fed successively through the cathode chamber and the anodechamber to produce an neutral anolyte (ANK) solution.
 11. The method ofclaim 1, wherein the current is at least 20 amps.
 12. The method ofclaim 1, wherein the current is at least 2.5 amps.
 13. The method ofclaim 1, wherein the liquid is supplied to both the anode and cathodecompartments at a lower part of the electrolysis cell and an anolyte anda catholyte are obtained from an upper part of the cell.
 14. The methodof claim 1, wherein a spiral feed of the liquid is fed to the anode andcathode compartments.
 15. The method of claim 1, wherein the current isa rectified square wave direct current is applied across the electrodes.16. The method of claim 1, wherein the first annular section comprisesan inlet fitting connected to an inlet tube that passes tangentiallythrough the first annular section of the end cap to communicate with theanode chamber through an aperture.
 17. The method of claim 16, whereinthe second annular section comprises an inlet fitting connected to aninlet pipe that passes through the second annular section of the end capto communicate with the cathode chamber through an aperture.
 18. Themethod of claim 1, wherein the second annular section comprises an inletfitting connected to an inlet pipe that passes through the secondannular section of the end cap to communicate with the cathode chamberthrough an aperture.